For registration of livestock, Japan has previously known the use of nose prints as with its cattle registration association and use of the pattern of black and white spots of Holstein dairy cattle as with its Holstein registration association.
On the other hand, Europe has used the pattern of spots for Holsteins in the same way as in Japan and also tattoos and ear punching. Recently, however, it has been registering dairy cattle using ear tags.
For breeding animals like dogs and cats, the method of management by implantation of a microchip storing a registration number is known. For ruminating animals, it is proposed to register them by making them ingest a microcapsule storing a registration number which will then remain in their stomachs.
While the registration of livestock using registration certificates as used for cattle in Japan was reliable, there was the problem that animals could not be confirmed in the field without the registration certificates and therefore quick confirmation of individuals was not possible.
Also, in the European method, the ear tag only carries part of the unique livestock registration number. While it is possible to issue a registration number unique to an individual on a national level, the practice  when confirming an individual at the time of registration is to only check the date of birth as calculated from the date of artificial insemination. Therefore, it is not possible to check whether the livestock in question is really the right one. This is because several calves are often born on the same day. Also, there are individual differences in the gestation periods. Accordingly, registering births using just the date of parturition as the check item easily results in errors. Further, even if the wrong information is entered, there is no means to find the error and correct it. Namely, there is the possibility of mistakenly registering a calf different from a blood line entered at the time of the artificial insemination.
A similar method is adopted for dogs as well. Critics have pointed to problems in its reliability as well.
That is, microchips, when initially developed, were said to be tamper-proof individual identifiers, but not only have there been mistaken attachment, breakdowns due to the fact they are industrial products and damage due to accidents, but also international standardization has made it possible for anyone to copy microchips even legally. Therefore, the reliability has been falling.
As explained above, conventional animal registration systems have had the problems that they are impractical if priority is given to reliability in identification of individuals and conversely are unreliable if priority is given to practicality.